This invention relates generally to the field of recording media, and in particular to systems and methods for making recording media. More specifically, the invention relates to novel ways to make flexible metal foil disks for storing computer data.
As known in the art, "hard" disk drives and "floppy" disk drives are the two major systems currently utilized with magnetic recording media. Copending U.S. patent application Ser. No. 09/007,452, filed Jan. 15, 1998 U.S. Pat. No. 5,968,627 the disclosure of which is herein incorporated by reference, describes exemplary metal foil disks for high data density recording. As described in that application, such metal foil disks are constructed differently than both conventional "hard" or rigid disks and "floppy" disks and offer an alternative to traditional storage media.
Rigid disks are formed by cutting a metal sheet and rod into individual circular shapes called substrate blanks and then subsequently processing the blanks by a set of discrete process steps. These process steps include steps to size and shape the substrate, polish, plate, texture, clean, coat by either vacuum deposition or spin coating, post-coat process, including lubrication, burnishing, inspection and testing. At each of these steps the disks are handled individually, either manually or by automated handling mechanisms. Such individual disk handling, whether manually or robotically, greatly increases the cost of the hard disk.
Floppy disks are processed in web form where a long sheet of the base material, typically mylar, is continuously passed through processing steps to clean, coat, dry, and lubricate the material. The disk shape is cut from the sheet after most of the processing is complete. This "web coating" process results in very inexpensive processing. See also, U.S. Pat. No. 5,122,392, the disclosure of which is herein incorporated by reference. However, such "web coating processes" produce disks with recording performance significantly inferior to hard disks. For example, the starting polymer material used to make the floppy disk cannot sustain the high temperatures typically used in the vacuum sputter deposition processes used for hard disks. Indeed, this is a key reason why the films applied to traditional floppy disk substrates have coercivities much lower than current hard disk processes. Due to the low degree of coercivity of the magnetic recording film, the floppy disk is unable to store large amount of data compared to a hard disk.
For example, a typical 95 mm diameter hard disk currently holds over 4.times.10.sup.9 bytes of data. In a hard disk drive this data can be read and written at a rate over 2.times.10.sup.7 bytes per second. However, a typical "high-performance floppy" disk of 95 mm diameter holds only 2.times.10.sup.8 bytes. These performance numbers are an order of magnitude less than the hard disk. In addition, during the coating operation for a floppy disk, the magnetic slurry must be continuously coated along the length of the sheet in order to create the uniformity required to make the finished disk properties acceptable.
Neither of the above two processes alone are well suited for producing thin flexible metal disks having the ability to store a high density of data. Hence, it would be desirable to provide systems and methods for making such thin flexible metal disks. The systems and methods should be efficient so that relatively large quantities of such disks may be economically produced.